[SalesForce] Cannot Return a List of Strings – Void method must not return a value

I've been using the notes from Simple Apex class to return a list of strings. I am having trouble getting this code to work. I'm writing a simple Apex Class as part of the Trailhead module Getting Started with Apex. Here's what I'm trying to do:

Create an Apex class that returns an array (or list) of formatted
strings ('Test 0', 'Test 1', …). The length of the array is
determined by an integer parameter.

The Apex class must be called 'StringArrayTest' and be in the public
scope.

The Apex class must have a public static method called
'generateStringArray'.

The 'generateStringArray' method must return an
array (or list) of strings. Each string must have a value in the
format 'Test n' where n is the index of the current string in the
array. The number of returned strings is specified by the integer
parameter to the 'generateStringArray' method.

Code

public class StringArrayTest {
    // Public Method
    public static void generateStringArray (Integer length) {
        // Instantiate the list
        String[] myArray = new List<String>();

        // Iterate through the list
        for(Integer i=0;i<length;i++) {
            // Populate the array
            myArray.add('Test ' + i);

            // Write value to debug the log
            System.debug(myArray[i]);
        } // end loop

        return myArray;
    } // end method
} // end class

Error Message

Void method must not return a value

Best Answer

You declared your return type as void. Change it to List<String>.

Incorrect

public static void generateStringArray

Correct

public static List<String> generateStringArray

It would be worth your time to read up on Class Methods:

To define a method, specify the following:

Optional: Modifiers, such as public or protected.

Required: The data type of the value returned by the method, such as String or Integer. Use void if the method does not return a value.

Required: A list of input parameters for the method, separated by commas, each preceded by its data type, and enclosed in parentheses (). If there are no parameters, use a set of empty parentheses. A method can only have 32 input parameters.

Required: The body of the method, enclosed in braces {}. All the code for the method, including any local variable declarations, is contained here. Use the following syntax when defining a method:
[public | private | protected | global] [override] [static] data_type method_name 
(input parameters) 
{
// The body of the method
}

It is your data_type that you have incorrectly specified as void in this case.

Related Solutions

[SalesForce] Simple Apex class to return a list of strings

You can't instantiate a List like that using an integer. You don't need to explicitly specify how much items are going into the list when it is created. Instead, just remove the integer:

//Instantiate the list
String[] myArray = new List<String>();

You're logic in your loop seems to be incorrect as well. Specifically, myArray's size will always be 0 when you instantiate it. Change your loop logic to:

for(Integer i=0;i<length;i++) {
   // code
}

You want to generate a List of strings based on the i variable. You will want to change your internal logic to:

//Populate the array
myArray.add('Test ' + i);

// Write value to the debug log
System.debug(myArray[i]);

Finally, you want to return that Array. You need to change your method so the return type is no longer void by changing its signature:

public static String[] generateStringArray(Integer length)

then it is just a matter of returning that array at the end of your method:

return myArray;

This would bring it all together as:

public class StringArrayTest {
    //Public Method
    public static String[] generateStringArray(Integer length) {
        //Instantiate the list
        String[] myArray = new List<String>();

        //Iterate throught the list
        for(Integer i=0;i<length;i++) {
            //Populate the array
            myArray.add('Test ' + i);

            // Write value to the debug log
            System.debug(myArray[i]);
        } //end loop

        return myArray;
    }//end method       
}// end class

Some more info on Arrays and Lists, Loops, and Class methods for future reference.

[SalesForce] Void or non-void method

This way you don't need to change your unit test class. But can test individual methods separately.

public without sharing class NPD_Opportunity_Cancel_Auto_Renew {
    public static void filter(Map<Id, Opportunity> oldMap, Map<Id, Opportunity> newMap) 
    {
        Set<Id> oppys = new Set<Id>();
        for(Opportunity o : newMap.values())
        {
            if( 
                o.StageName != oldMap.get(o.Id).StageName &&
                o.Stagename == 'Cancelled' 
            )
            {
                oppys.add(o.Id);
            }
        }

        List<Opportunity> oppsToCancel = getOpps(oppys);
        updateOpps(oppsToCancel);
    }


    public static List<Opportunity> getOpps(Set<Id> oppys)
    {
        // Find related Opps where the Revnewed From is in the oppys list
        List<Opportunity> oppsToCancel = new List<Opportunity>();       oppsToCancel = [SELECT    Id,
                                StageName,
                                Renewed_From__c
                        FROM    Opportunity
                        WHERE   Renewed_From__c IN : oppys];

        return oppsToCancel;
    }


    public static void updateOpps(List<Opportunity> oppsToCancel)
    {
        for(Opportunity oppy : oppsToCancel)
        {
            oppy.StageName = 'Cancelled';
        }

        try 
        {           
            update oppsToCancel;        
        }       
        catch(Exception exp)        
       {            
           System.debug('Error on update' + exp);       
        }
    } 
}

Best Answer

Related Solutions

[SalesForce] Simple Apex class to return a list of strings

[SalesForce] Void or non-void method

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